It never failed to amuse Amphitrite that humans tried so hard to conquer the sea. They voyaged out in their little boats and fought the waves to explore new lands, trade goods, or plunder the depths for the bounties it offered. She watched them sometimes, amused as a child might be observing ants going about their tiny little lives, but rarely did she take interest in individuals. If a single human on a ship disrespected her realm, she might drown the lot of them. Likewise, if a handful of humans in a fleet of ships pleased her enough, she might give them favourable conditions on their journey and see them safely to their destinations, or given them the edge in a battle with her waves.
All this to say her relationship with humans was ephemeral at the best of times, and often steered by her mood. So to focus on one human was certainly not something she was known to do, especially when said human did nothing to draw her attention other than exist. And yet, that's the situation the goddess finds herself in.
Pirates were often fun to observe, full of superstition and often holding respect for the seas they prowled, but they were always men. Most humans on the sea were men, but pirates especially, so to find a woman pirate... Well, Amphitrite had been quite interested. She'd watched this unusual mortal for some time, never really inteferering, but checking in from time-to-time to see how she fared among her rough male counterparts. The answer was; fairly well, or as well as a woman could do amongst the morally dubious ship of pirates. She considered once or twice on making contact, but she remained distant and impartial, just observing, never inteferering. Until, of course, the woman had ended up overboard with several others as a storm raged above.
The queen of the seas should've left her to her fate, but that interest - that draw - finally made her act directly. Enveloping the woman's body in her embrace, Amphitrite spirited her away from the churning waters to safety - an uninhabited island humans had yet to plunder and claim like they did all other land masses they discovered.
It's there in the shallows, holding the human from behind against her mermaidic form, that she commands the water to leave the woman's lungs, drawing it from her throat to allow her to suck in air once more.